This invention relates generally to the field of telephone protection modules used in a central office for protecting office equipment from excess current surges on individual subscriber pairs, and more particularly to a replacement type protector module adapted for use with certain types of older telephone protector blocks using a generally cylindrically shaped protector module, a typical example being the Western Electric Type 300 block and associated modules.
In this type of block, the module is of cylindrical configuration and engages a bayonet type spring socket somewhat resembling that employed for a small base incandescent lamp. The carbon block element is aligned with the axis of the module, and is resiliently clamped between a pair of peripherally oppositely disposed spring fingers which conduct to one of the carbon blocks. Providing secondary protection, the modules are usually provided with heat sensitive means in the form of a coil which melts a solder pellet to provide for bypassing the air gap using constructions which are well known in the art.
With the continued improvement in quality and availability of gas tube type air gap means, almost all new installations now feature this type of protection. In older constructions, principally due to the lack of availability, replacement modules have been constructed substantially identical to the modules which they replace, e.g. utilizing old type carbon block protection.